The present invention relates to a rear wheel suspension for motorcycles which is formed by fitting a suspension coil spring into a hydraulic damper of telescope type consisting of inner and outer telescopic tubes.
In conventional motorcycle front wheel suspensions, as seen in Japanese Utility Model Publication Nos. 27406/1973 and 1163/1974, for instance, use is commonly made of a front fork formed by fitting a suspension coil spring into a hydraulic damper of telescope type consisting of inner and outer telescopic tubes. However, a few hydraulic dampers of this type which also work as a suspension are used for the rear wheel suspension of motorcycles.
The reason may be explained by the following. First of all, in the case of motorcycles, the rear wheel normally receives a larger load than does the front wheel, making it common practice to use in the rear wheel suspension a strong coil spring having a spring constant 1.5-1.8 times higher than that used in the front wheel suspension. This inevitably makes the suspension coil used in the rear wheel suspension larger in wire diameter than that used in the front wheel, suspension, and consequently, the said suspension coil spring hinders the working oil flow in the hydraulic damper when the rear wheel suspension is in operation so that its damping characteristics deteriorate. Next, in the case of rear wheel suspension which is more closely related to the riding comfort of motorcycles, it is desirable, in order to retain a good feeling, that the Road of the suspension coil spring be minimized when the hydraulic damper is extended close to the maximum. To this end, use could be made of an additional spring member that would counter the suspension coil spring when the hydraulic damper was extended close to the maximum, or otherwise, the suspension coil spring could be set beforehand so as to reach its normal length when the hydraulic damper is extended to the maximum. The former measure is difficult to practice spatially however, because the rear wheel suspension has a strict limitation in total length, differing from front wheel suspensions, while the latter measure causes the suspension coil spring, as it has received a permanent setting, to jolt in the hydraulic damper every time it is extended to the full, and this rather impairs the feeling of the suspension not only degrading the riding comfort but also generating noises unpleasant to the rider.
Nonetheless, if these defects could be resolved, and if a rear wheel suspension of this type could be realized, there would be the significant merit that mass-production would be made possible through minimizing of the changes in the production arrangements required to make best use of the similarity between the structural parts of the front wheel and rear wheel suspensions.